Solvent extraction of water-immiscible, oil-soluble alcohols with liquid hexanetriol



SOLVENT EXTRACTION OF WATER-IMNIISCIBLE,

OIL-SOLUBLE ALCOHOLS WITH LIQUID HEX- ANETRIOL Joseph R. Kenton, Texas City, Tex., ass'ignor, by mesne assignments, to Standard Oilv Company, Chicago, Ill., a corporation of Indiana No Drawing. Filed Dec. 23, 1957, Ser. No. 704,310

9 Claims. (Cl. 260-450) The present invention relates to the extraction of oilsoluble, water-immiscible alcohols from normally liquid hydro-carbons, and particularly concerns the useof liquid hexanetriol as a selective solvent for this purpose.

An object of the present invention is to provide a method for removing dissolved water-immiscible alcohols from mixtures thereof with liquid hydrocarbons. Another object is to provide a method for removing such alcohols from mixtures thereof with liquid hydrocarbons and organic carbonyl compounds. A further object is to provide a method for recovering valuable oil-soluble chemicals from the products of hydrogenation of carbon monoxide in the presence of an iron catalyst. Other objects and advantages of the invention will be apparent from the detailed description thereof.

It has been found that oil-soluble alcohols can be extracted from a mixture of the alcohol with normally liquid hydrocarbons by employing liquid hexanetriol, e.g. 1,2,6-hexanetriol as the selective solvent. Mixtures such as cannot readily be separated by distillation due'to the closeness of the boiling points of the hydrocarbon and alcohol or because of azeotrope formation are readily separated by extraction with this solvent.

going separation. The oil-soluble products obtained'from the hydrogenation of carbon monoxide using an iron catalyst can be extracted with the liquid hexanetriol, after carboxylic acids have been removed from "the oil-soluble products, thereby extracting valuable oil-soluble alcohols and simultaneously purifying the hydrocarbons and rendering them more suitable for subsequent processing.

Hexanetriols, which may be either 1,2,6- or 1,3,6-hexanetriol, have very high boiling points and'low freezing points. 1,2,"6-hexanetriol has'a boiling point of 178 C. 'at mm. Hg abs., a'freezing point of 20"' C, and a specific gravity of 1.1063 at 20 C.

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2 range mixture. The present invention is particularly useful for separating mixtures which cannot ordinarily be separated by distillation due to the closeness of boiling points of the hydrocarbon and alcohol or because azeotropes are formed between the hydrocarbon. and alcohol.

Chemical manufacturers often have mixtures of waterimmiscible, oil-soluble alcohols with normally liquid hydrocarbons. Such mixtures are formed during the oxidation of hydrocarbons such as paraflinic and/or olefinic hydrocarbons. They are also formed during the hydrogenation of carbon. monoxide by the Fischer-Tropseh process and its various modifications. As an example of this type process, carbon monoxide and hydrogen are contacted with an ironcatalyst at a temperature between about, 450 to 750 F. and a pressure between about 100 to 700 p.s.i.g. Streams of water-soluble and oil-soluble chemicals are produced. The water-soluble alcohols may readily be recovered from the products by Water washing techniques, but the oil-soluble alcohols are difficult to remove from the hydrocarbons Which are produced during the process. The oil-soluble organic chemicals, which form a homogeneous solution in the liquid hydrocarbons, consist of carboxylic acids, alcohols, aldehydes and ketones, and a small amount of esters. The composition of such a stream is given in. Industrial and Engineering Chemistry, volume 45, pages 359-362 (February 1953). The carboxylic acidsmay be removed from the hydrocarbon stream containingthe oil-soluble chemicals by extracting with aqueous solutions of sodium carbonate, or by other techniques. Thereafter the hydrocarbon stream of oil soluble chemicals may beextracted with liquid hexanetriol to remove the alcohols from the hydrocarbons.

The liquid hexanetriol can be used inthe solvent extraction of mixtures of normally liquid hydrocarbons and 'oil- 'soluble, water-immiscible,alcohols. The extract phase of hexanetriolis richin extracted alcohols and thehydrothis manner oil-soluble alcohols, which are; essentially immiscible with Water, such as'contain from about 4 to 15 carbon atoms per molecule can be extractedfrornnormally liquid l'iydrocarbons.v The particular type of hydrocarbon presenthas no criticalbearinguponthe extraction procesgand it may be an aromatic, cyclo-aliphatlcoralicarbon. rafiiniatephase is depleted in the alcohols. In

Either a wide boiling range portion, of the oil-soluble chemicals stream may be extracted, or a narrow boiling mixture may be extracted This solvent is quite selective forextracting the alcohol from the'hydrocarbon. It has only slight'effectiveness for extracting aldehydes and ketones from the hydrocarbons. used to extract alcohols from aldehydes and/or ketones.

When it is desired to remove the maximum amount of the various oil-soluble oxygenated hydrocarbons present in the hydrocarbon stream containing dissolved alcohols, carbonyl compounds, etc. from the Fischer-Tropsch process or from similar streams from hydrocarbon oxidation processes, the hydrocarbon oil containing the dissolved oil-soluble oxygenated hydrocarbons may be selectively hydrogenatedt'o convert aldehydes and ketones therein to alcohols. Because alcohols are extracted by liquid hexanetriol with high efiiciency, a more complete purification of the hydrocarbons is obtained during the solvent extraetion step. This-renders the raffinate hydrocarbon phase more suitable for subsequent use or processing such as deoxygenation and conversion to gasoline constituents. The hydrogenation may be carried out attemperatures of 50 to 150 C. using catalysts such as nickel or kieselguhr or copper chromite and thereby effecting conversion of the carbonyl compoundto the alcohol Without any sub stantial conversion of alcohols to hydrocarbons. Methods taught in US. 2,760,994 and in the text Reactions of Hydrogen by H; Adkins, pages 8, 11, University of Wisconsin Press (1937).

for effecting selective reduction-of a'jcarbonyl group are .In general, liquid liquid extraction operations can be I carried out with the hexanetriol at temperatures of from somewhat above itsfmelting' point up to the boiling point 'of the charge mixture; for example, temperatures of range' f O" to'IO OFlCJmayfbeusedj The particular tern "'perat'ure used will' depend' upon the'particular charging stock, the solvent: feed ratio, thenumberof extraction Thus it may also be r refining art.

Certain solvent extractions were carried out which stages, the degree of extraction which is sought, the proportions of auxiliary solvents or countersolvents, etc.

The ratio of solvent to the charge mixture of hydrocarbons and alcohol undergoing separation, must be sufficient to exceed the solubility of the solvent in the charge stock in order to form two distinct liquid phases, viz. a raffinate phase of hydrocarbons containing little if any solvent, and an extract phase of solvent containing the alcohols as the solute. Generally, between about 0.2 to voumes of solvent may be used per volume of the charge mixture which is to be separated. Equal volumes of solvent and charge mixture constitute a very satisfactory ratio. A small amount of water, e.g. 1 to 20% based on solvent, may be introduced into the extraction zone (either separately or together with the solvent) to increase the selectivity of the solvent for extracting alcohols. To increase the selectivity for removing alcohols in preference to hydrocarbons or carbonyl compounds such as aldehydes and ketones, a hydrocarbon countersolvent may be used. This countersolvent is preferably one which boils outside the boiling range of the charge mixture undergoing separation and outside the boiling range of the solvent. In this way it can be fractionated to separate it from the hydrocarbon raftinate phase and the extract phase (when any amounts are left in this latter phase). The countersolvent may be used during the extraction process by introducing it into the extraction zone so that it scrubs the extract phase as it passes through the extraction zone. In this manner it scrubs out the carbonyl compounds and any minor amounts of hydrocarbons which may have been extracted from the charge mixture. Washing with the hydrocarbon countersolvent may also be carried out after the extract phase has been separated from the raffinate phase. In this manner the separated extract phase may be scrubbed in a tower or other suitable equipment to remove the extracted carbonyl compounds and hydrocarbons from the extract phase. The very high boiling point of the hexanetriol makes it advantageous to use in solvent extraction, particularly when a Wide boiling range charge mixture containing very high boiling alcohols is extracted. For example, the stream of oil-soluble products from the Fischer-Tropsch process contains alcohols which boil from as low as 100 C. up to and above 300 C. While other solvents boil somewhere within the broad boiling range of the alcohols (most solvents have boiling points between 100? to 250 C.), the hexanetriols have a higher boiling point than any of the alcohols produced in the Fischer-Tropsch process. Because of this, the alcohols can be recovered from the extract phase by distilling them overhead, leaving the solvent behind as bottoms. With the other known solvents the boiling range of the charge mixture must be carefully controlled in order to be able to separate the alcohols from the extract phase by distillation. Other techniques besides distillation may be used to recover the alcohols from the solvent, e.g. washing the extract phase with water to dissolve out the solvent while leaving the alcohols behind, 1

and then recovering the solvent from the water; but such techniques require additional distillation columns. Likewise, any dissolved solvent can be recovered from the raffinate phase by washing with water. The extraction process can be carried out in a batch,'continuous or semicontinuous manner, and in one or more actual or theoetical stages, employing contacting equipment such as has heretofore been employed in the selective solvent are illustrative of the present invention. A mixture of hydrocarbons and -oil-soluble oxygenated compounds which wasprepared by the hydrogenation of carbo'nmon- ,oxide in the presence of an iron catalyst (modified Fisclzer-Tropsch process) was obtained. The carboxylic fz cids had-beenrerrio'ved from this mixture, and the mixture had been fractionated 'to obtain 158-187? C. fracf ing a scrubbed a tion which was used as the charging stock employed in the solvent extraction step. The fraction charged to the solvent extraction step consisted of approximately 69 volume percent C1041 olefins, 13 volume percent saturated hydrocarbons, 8 volume percent aromatics, and 10 volume percent oxygen-containing hydrocarbons. The saturated hydrocarbons, aromatics, and oxygen-containing hydrocarbons boiled within the same range as the C1041 olefins. The alcohols, which were primarily C alcohols, comprised about half of the oxygen-containing hydrocarbons, aldehydes comprised the next largest portion of the oxygen-containing hydrocarbons, and the remainder consisted primarily of ketones with a minor amount of other oxygenated hydrocarbons. A portion of the above defined mixture was shaken with an equal volume of 1,2,6-hexanetriol at 50 C. 'Thereafter, a raffinate layer was separated from an extract layer. Analysis of the rafiinate, after washing with water to remove any dissolved solvent, indicated that 67% of the alcohol had been extracted therefrom. Analysis of theraffinate further indicated that only about 26% of the aldehydes and ketones had been extracted from the charge mixture. The fact that the rafi'inate comprised 94% by volume of the charge mixture, coupled with the fact that 67% of the alcohols had been extracted therefrom, shows that the solvent is extremely selective and extracts essentially no hydrocarbons. This is another distinct advantage when practicing this invention. Another portion of the charge mixture was extracted five times with 20 volume percent (based on charge mixture) of 1,2,6-hexanetriol at C. Approximately the same results were obtained.

Thus having described the invention, what is claimed 1. A method for refining a mixture comprising normally liquid hydrocarbons and oil-soluble water-immiscible alcohols, which process comprises selectively extracting said mixture with liquid hexanetriol, and separating a. liquid extract phase containing oil-soluble water-immiscible alcohols.

2. The method of claim 1 wherein the hydrocarbonalcohol solution is not readily separable by distillation.

3. The method of claim 1 wherein the mixture which is extracted with said liquid hexanetriol is produced by hydrogenating carbon monoxide in the presence of an iron catalyst and thereby producing water-soluble oxygenated organic compounds, water-immiscible oil-soluble oxygenated organic compounds and hydrocarbons, recovering a mixture of hydrocarbons containing dissolved water-immiscible oil-soluble organic oxygenated compounds comprised of carboxylic acids, alcohols, aldehydes and ketones, removing carboxylic acids from the mixture of hydrocarbons and dissolved oil-soluble organic oxygenated compounds, and thereafter extracting with liquid hexanetriol the mixture of hydocarbons and organic oxygenated compounds from which carboxylic acids had been removed. 7

4. The method of claim l wherein the mixture of hydrocarbons and alcohols contains aldehydes, said mixture is hydrogenated to convert aldehydes to alcohols, and the hydrogenated mixture is thereafter extracted with liquid hexanetriol. v 5. The method of claim 1 wherein the hexanetriol is 1,2,6-hexanetriol.

6. A method for refining a mixture comprising normally liquid hydrocarbons and oil-soluble water-immiscible alcohols boiling below the boiling point of liquid hexanetrioland organic carbonyl compounds which process comprises agitating said mixture with an amount of liquid hexanetriol sufiicient to form distinct extract and raffinate phases, washing said extract'phase with normally liquid hydrocarbons and thereby scrubbing'organic'carbonyl compounds from said extract phase, and recoverextract phase of hexanetriolr rich'in alcohol. I g l 7. The method 'ofclaim 6-wherein the liquid Hydrop ruv.

carbon employed in scrubbing the extract phase boils at a temperature outside the boiling range of the components of the mixture charged to the refining step.

8. A method for selectively extracting oil-soluble water-immiscible alcohols containing from about 4 to 15 carbon atoms from a mixture containing said alcohols and normally liquid hydrocarbons, which method comprises extracting said mixture with a liquid hexanetriol selected from the group consisting of 1,2,6- and 1,3,6- hexanetriol, separating the resulting liquid extract phase from the resulting rafiinate, said extracting and separating being selective to oil-soluble water-immiscible alcohols in preference to oil-soluble carbonyl compounds, and recovering said oil-soluble water-immiscible alcohols from said hexanetriol solvent by distillation.

9. A process for the liquid-liquid selective extraction of oil-soluble water-immiscible alcohols from a 158 C.

to 187 C. fraction of a product resulting from the hydrogenation of carbon monoxide and containing normalvolume of 1,2,6-hexanetriol per volume of said fraction References Cited in the file of this patent UNITED STATES PATENTS 2,059,495 Smeykal Nov. 3, 1936 2,205,184 Woodhouse June 18, 1940 2,542,454 Arnold et a1. Feb. 20, 1951 2,543,038- McGrath Feb. 27, 1951 2,558,556 Hess et a1. June 26, 1951 2,581,712 Rottig Ian. 8, 1952 2,615,912 Michael Oct. 28, 1952 2,625,560 Michael Ian. 13, 1953 2,664,435 Burton et a1. Dec. 29, 1953 Mapes et a1. Aug. 5, 1958 

9. A PROCESS FOR THE LIQUID-LIQUID SELECTIVE EXTRACTION OF OIL-SOLUBLE WATER-IMMISCIBLE ALCOHOLS FROM A 158*C. TO 187*C. FRACTION OF A PRODUCT RESULTING FROM THE HYDROGENATION OF CARBON MONOXIDE AND CONTAINING NORMALLY LIQUID HYDOCARBONS, OIL-SOLUBLE WATER-IMMISCIBLE CARBONYL COMPOUNDS, AND SAID OIL-SOLUBLE ALCOHOLS, WHICH PROCESS COMPRISES EXTRACTING SAID FRACTION WITH ABOUT ONE VOLUME OF 1,2,6-HEXANETRIOL PER VOLUME OF SAID FRACTION AT A TEMPERATURE OF ABOUT 50*C. WHEREBY OF SAID FRACTION BLE WATER-IMMISCIBLE ALCOHOLS ARE SELECTIVELY OBTAINED IN PREFERENCE TO SAID OIL-SOLUBLE CARBONYL COMPOUNDS IN A LIQUID 1,2,6-HEXANETRIOL EXTRACT PHASE, SEPARATING THE RESULTING LIQUID EXTRACT PHASE FROM THE RESULTING LIQUID RAFFINATE PHASE, DISTILLING THE EXTRACT PHASE TO A TEMPERATURE UP TO AND ABOVE 300*C. AND RECOVERING OIL-SOLUBLE WATER IMMISCIBLE ALCOHOLS FROM THE EXTRACT PHASE IN AN OVERHEAD FRACTION FROM SAID DISTILLING WHILE LEAVING SAID 1,2,6HEXANETRIOL IN A BOTTOMS FRACTION FROM SAID DISTILLING. 